I regularly use my Twiddler with my Android phone. It allows me to fully operate all the applications I use on my desktop computer, e.g. Emacs.
https://www.mytwiddler.com/
I have a twiddler and tried doing this a long time ago i.e. emacs with a twiddler. For me I really needed to use a sticky cntl and alt key because I just couldn't press the cntl button on the top and chord at the same time. And I couldn't figure out how to make the sticky cntl work on the phone. But that was a very long time ago. Now I just use a mini bt keyboard and termux to run emacsclient over ssh and that's good enough for what I want.